We listen to music with a lot of unconscious preconceived notions depending on our upbringing. Our brains enjoy grouping, repetition, structure. Also tension in the form of expectations and surprises. We can make music in free time without these patterns but to most of us it sounds less 'normal'. It's like if we make music with pitches in between the 12 notes of western tradition.

A lot of those preconceptions are to do with the stresses in a bar/measure. Things like when drums are hit or when melodies begin and progress. Misusing this leads to the same effect as stressing the wrong syllables in speech. Something like a waltz (which is 3/4) depends on stresses in a pattern of 3 beats, matching the dance. If you write a waltz as the same notes in 4/4 the patterns that should align on 3rd notes will not relate to the written form. Stresses are also why 3/4 and 6/8 are distinct - they are identical in values but the grouping of notes is not. They can also differ because the actual rhythm as played can differ from how it is written i.e. swing.

If you imagine the melody along with 'twinkle twinkle little star' and stop, it should feel unresolved because of the note it ends on. You need 'how I wonder what you are' to feel comfortable again. These two phrases should have a relation and similar grouping. It's harder to notice but within each of these phrases there's a pair of bars that have a similar relation.